Many types of wheelchairs are known in the prior art. Conventional wheelchairs are propelled by either a person pushing the wheelchair to transport the chair's occupant or by the occupant himself or herself, typically by grasping the main wheels of the chair to turn them. Of course, it is also known to provide wheelchairs with an auxiliary propulsion system such as a battery powered electric motor. Wheelchairs have also been proposed wherein the person in the chair can propel the chair by pushing foot pedals associated therewith or by pushing or pulling hand powered mechanisms.
The following patents are believed to be generally representative of the current state of the prior art relating to wheelchairs: U.S. Pat. No. 5,280,937, issued Jan. 25, 1994, U.S. Pat. No. 4,537,415, issued Aug. 27, 1985, U.S. Pat. No. 5,174,418, issued Dec. 29, 1992, U.S. Pat. No. 4,371,183, issued Feb. 1, 1983, U.S. Pat. No. 5,244,223, issued Sep. 14, 1993, U.S. Pat. No. 4,592,570, issued Jun. 3, 1986, U.S. Pat. No. 3,953,054, issued Apr. 27, 1976, U.S. Pat. No. 4,586,723, issued May 6, 1986, and U.S. Pat. No. 5,020,815, issued Jun. 4, 1991.